Why does the thickness of the earth's crust vary widely between continental masses and the ocean?
Answers
Answer:
These varying thickness of earth's crust is basically due to continuous disturbances occurring beneath the earth crust. Our earth is consists of three layers, i.e., 1)Crust 2)mantle 3)core. ... So, due to molten core the inner layer of mantle also get heat up and become molten too and start moving towards the surface.
Explanation:
Why does the thickness of the earth's crust vary widely between the continental masses and the ocean floor?
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Our earths crust is devided into continental crust and oceanic crust. the continental crust is rich in Si and Al.. hence called SiAl, and oceanic crust is richer in Si and magic minerals,hence called SiMa. The oceanic crust is very young and continuously generated at the mid oceanic ridges and consumed at subduction zones. Due to denser composition, the oceanic plate subducts into the asthenosphere. And Continental plate cannot (lighter composition). As subduction of oceanic plate ( contains crust and upper part of upper mantle) occur, the sediments deposited in the basin that is being closed, are acreated to huge fold mountains (continental crust) moreover the oceanic crust on descent into the asthenosphere ungergoes partial melting forming arc mountains. Hence if we see the whole scenario,
Oceanic crust —> continental crust +remelted oceanic crust. (—-> : melting and partial melting)
And the continental crust never generally gets consumed in any tectonic process. Hence the thickness of continental crust consequently increases where as oceanic crust remains thin and constant.
These varying thickness of earth’s crust is basically due to continuous disturbances occurring beneath the earth crust.Our earth is consists of three layers, i.e., 1)Crust 2)mantle 3)core.
Mantle is consists of hard bedrock, while core consists of molten lava made of alloy of iron and nickel. So, due to molten core the inner layer of mantle also get heat up and become molten too and start moving towards the surface. But, during this movement this molten material loses it’s heat and get solidified again. This process keeps on repeating and is termed as convection currents. These convection currents results in continuous shifting of tectonic plates, which causes non uniform earth crust.
the thinnest layer of earth’s crust is present at the point where volcanoes are rises above the ground surface.
It is essentially because the oceanic crust is much younger than continental crust.
The crust below the ocean is constantly being recycled at subduction zones. This is where it is plunged below the continents and back into the mantle, due to being denser than the continental rocks. This is what happens to the West of the Andres in Sth america, the Nazca plate (oceanic) is moving east and bends underneath the sth american plate, creating the beautiful mountain range you see. This recycling comes full circle at the other end of the Nazca plate, where it is separating from the pacific plate- this is where mantle material comes to the ocean floor and becomes young, dense oceanic crust and the cycle continues.
Continental crust is less dense so cannot be subducted below other crust, where continental crust collisions happen you get large mountain ranges (Himilayas, european alps). This thickening is associated with substantial thickening below the surface also (see Isostasy for the explanation why) causing such a dramatic difference in width.